Fig8_12 Abundance of the elements in the Sun

Fig. 8.12 . The relative abundance of the elements in the solar photosphere, plotted as a function of their atomic number Z, which is the number of protons in the atomís nucleus and roughly half the atomic weight. The abundance is plotted on a logarithmic scale and normalized to a value a million, million, or 1.0 x 1012, for hydrogen. Hydrogen, the lightest and most abundant element in the Sun, was formed about 14 billion years ago in the immediate aftermath of the big bang that led to the expanding universe. Most of the helium now in the Sun was also created then. All the elements heavier than helium were synthesized in the interiors of massive stars that no longer shine, and then wafted or blasted into interstellar space where the Sun subsequently originated. Carbon, nitrogen, oxygen and iron, were created over long time intervals during successive nuclear burning stages in former massive stars, and also during their explosive death. Elements heavier than iron, were produced by neutron capture reactions during the supernova explosions of stars that lived and died before the Sun was born. The light elements boron, beryllium and most of the lithium are believed to originate from heavier cosmic-ray particles that have been stripped of some of their ingredients by collisions, in a process called spallation. The exponential decline of abundance with increasing atomic number and weight can be explained by the rarity of stars that have evolved to later stages of life. (Data courtesy of Nicolas Grevesse.)